U.S. Pat. No. 4,668,129 (Babcock et al), the entire contents of which is incorporated herein by reference, discloses a modular precast concrete retaining wall system that utilizes rigid counterfort elements that interact with the surrounding backfill or bulk material to redistribute stresses within the retained soil mass. Although the wall configurations disclosed in the above referenced patent are capable of providing high stable retaining walls, none of the walls provide a smooth visually unbroken face. This is because the concrete retaining wall panels are supported at each end by bearing directly upon the vertical columns of each adjacent precast concrete counterfort. These column portions must be of sufficient thickness and strength to withstand the transmitted earth loads from the wall panels retaining the earth mass. The wall configurations of U.S. Pat. No. 4,668,129 typically result in substantial protruding vertical columns that are regularly spaced vertically or horizontally along the length of the retaining wall. Many situations preclude the use of such a retaining wall configuration. For example, if directly next to a roadway the protruding vertical concrete columns may be deemed to be a dangerous obstruction or if columns are incompatible with architectural aspects of the facing.
U.S. Pat. No. 4,655,646 (Babcock et al), attempts to overcome the problem of exposed vertical counterfort columns by providing configurations that hold prestressed wall panels with horizontal continuous precast concrete beams placed at the base and top of the precast concrete counterforts. While the configurations provided by U.S. Pat. No. 4,655,646 eliminate the vertical counterfort columns the disclosed configurations still do not provide a smooth unbroken architectural face. Also, the wall configurations of U.S. Pat. No. 4,655,646 require additional precast beam components which are expensive and difficult to transport and handle. Erection proves most difficult and construction tolerances are greatly reduced.
There are also some prior art retaining wall systems that provide a smooth faced retaining wall structure but none afford the geotechnical engineering benefits of the systems disclosed by U.S. Pat. Nos. 4,668,129 and 4,655,646.
For example, U.S. Pat. No. 4,884,921 discloses a modular "T" unit that can be stacked in multiple configurations to create a smooth faced retaining wall system. However, the stacking of these "T" units creates a brick bonded system from the top to the bottom of the wall system. This direct stacking of the modular units without backfill between adjacent vertical units precludes soil arching and provides none of the desired geotechnical benefits disclosed by U.S. Pat. No. 4,668,129.
It would, therefore, be desirable to provide a modular precast retaining wall system that simply and economically provides a smooth faced retaining wall but maintains the geotechnical design advantages of the wall system of U.S. Pat. No. 4,668,129.